Q.series
Gantner Instruments GmbH
135
6 Functional Procedures → Using serial interfaces
6 Functional Procedures
This chapter explains various important settings and processes
more comprehensively than in the previous chapters, for exam-
ple, to provide you with decision-m
aking aids for the interface
parameters or the settings of the modules.
6.1 Using serial interfaces
The interface on the Q.bloxx modules is based on the RS-485
standard. This means that data transmissions over distances up
to 1 km and the connection of several devices to one in
terface is
possible; the RS-485 interface is therefore a bus-type interface.
With the Q.series up to 16 devices (modules) can be connected
per b
us segment.
PCs are however usually “only” equipped with one RS-232 inter-
face with which, according to the standard, a maximum line
lengt
h of 20 m is admissible and only one device can be connected
per inte
rface. Therefore for communication with the Q.bloxx
modules you need either an RS-485 interface card in the PC or an
inte
rface converter.
One technique is particularly important to facilitate large line
le
ngths: the so-called bus termination. This comprises resis-
tances which must be connected in the lines, so that no reflec-
tions occur at the line terminations i.e. the resistances attenuate
the signal at the
end of the line.
You will find further information on
these topics and on connec-
tion techniques in this section.
6.1.1 Interface converter
Gantner Instruments GmbH offers you two different interface
converters:
1. The compact interface converter ISK 200 (bench-top unit)
The converter has an integrated power supply for the con-
nected modules and automatic baud rate detection. The
power supply v
ia the 230 V mains, the bus connection and the
output voltage of 24 V
DC
are electrically isolated from one
another.
2. The interface converter ISK 101
The converter is integrated directly into an interface cable.
Th
e terminating resistance is also located in the connecting
plug and is always active.
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